1. Field of the Invention
The present invention is based on known glow plugs and methods for manufacturing such glow plugs.
2. Description of Related Art
Glow plugs, in particular sheathed-element glow plugs, are suitable in particular for use in internal combustion engines, for example, for use for cold start of diesel engines or other engines, in particular spontaneous ignition internal combustion engines. Glow plugs may also be used in other areas of combustion technology.
A known example of glow plugs and in particular sheathed-element glow plugs is described in published European patent application EP 1 768 456 A1, where a ceramic heating body is used as the sheathed element, heating wires and a heating resistor being situated inside thereof. One of the heating wires is contacted from the circumferential side of the heating body. The other heating wire is led axially out of the glow pencil-shaped heating body as a terminal contact via an extension.
However, one problem with known glow plugs, in particular sheathed-element glow plugs made of silicon nitride (Si3N4), involves electrical contacting of the terminal contacts. For example, glow plugs made of silicon nitride are often contacted via a comparatively sensitive metal “cap connection” by which the terminal contact in the form of a wire, for example, is held on the ceramic. The wire is led into a housing of the glow plug, where it is connected to a terminal pin, e.g., by screwing, spot welding, crimping or similar joining techniques. Next the housing is filled with a ceramic powder filling, and the fixation between the wire and the terminal pin is reinforced by hammering the housing.
However, there are a number of technical challenges for this manufacturing operation in practice. First, the filling of the housing with the ceramic powder, followed by the hammering operation, is comparatively complex. Another problem is that the sensitive heating bodies, for example ceramic heating bodies, may be damaged in the hammering operation.